The present disclosure generally relates to the field of building automation systems. The present invention more particularly relates to systems and methods for sensing dew point using a temperature sensor and a humidity sensor.
Condensation or dew may occur on a surface when the temperature of the surface is lower than the dew point temperature of the air. Condensation on the surface may collect and cause dripping onto the “working” space below the surface. Condensation can be problematic when the working space underneath the surface is sensitive to moisture. For example, the working space may have documents, electrical equipment, and other items that may be damaged or destroyed when exposed to moisture.
In applications where there is a cooled and exposed surface in a zone, it is important to keep the dew point of the zone below the temperature of the surface or the temperature of the surface above the dew point of the zone. Condensation may occur in numerous places in a building space. For example, condensation may occur on exposed pipes. Condensation may also arise in chilled beam cooling systems. Chilled beam cooling systems employ pipes of cool water passed through a beam near the ceiling to cool air in the zone. Natural convection and/or supplemental heating, ventilation, and air conditioning (HVAC) systems are used to circulate the conditioned air to the lower, working space of the zone. Because the heat exchanger is exposed to working space below, it is necessary to monitor the dew point in the zone when chilled beam cooling is working. Chilled beam cooling systems may be passive or active. Active chilled beams may include components (e.g., air handling unit, fans, ducts) for delivering a supplemental air supply into the zone. The supplemental air supply may be pretreated to control ventilation, temperature, and/or humidity in the zone. The supplemental air supply may act to induce air in the zone across the heat exchanger. Passive chilled beams may not include a supplemental air supply to induce movement of air in the zone and rely on natural convention for air movement.
Problems associated with condensation may be solved with proper monitoring and control of the dew point. However, dedicated dew point sensors can be prohibitively expensive when needed to monitor the dew point in many zones. Additionally, the uncertainty in the dew point measurement by a dedicated dew point sensor is non-zero and may not be specified by a manufacturer.